1. Field of the Disclosure
Improved calcium phosphate cements are well tolerated by the body. These improved cements include a non-covalently bonded interpenetrating network.
2. Description of the Background of the Disclosure
Calcium phosphate composites are used as bone substitutes and bone grafts. These calcium phosphate composites tend to form complexes primarily between calcium-based salts through charge interactions. These composites are used as general bone void fillers and generally lack the adhesive strength sufficient to adhere or fix bones together, for example, fractured surfaces. These prior compositions have insufficient chemical interaction between the calcium phosphate composite and the bone surface or other surface materials and lack sufficient strength to be used to attach bone to bone or bone to other materials.
Certain marine species, such as tubeworms and sand castle worms, rely on secreted proteins containing a high amount of the amino acid phosphoserine for adhesion mechanisms (“The tube cement of Phragmatopoma californica: a solid foam,” Russell J. Stewart, James C. Weaver, Daniel E. Morse and J. Herbert Waite, Journal of Experimental Biology 207, 4727-4734, 2004). The specific mechanism of the phosphoserine involvement with the proteins is not understood; however, phosphoserine has been reported to be responsible for a specific interaction with calcium containing hydroxyapatite of bone as disclosed in U.S. Patent Application Publication No. 2005-0217538A1. In this publication, the authors mention calcium phosphate cements modified with phosphoserine (from 0.5% to 5% weight of the formulation) to aid as a compressive strength and surface area modifier in the bone cement material. In this range (from 0.5% to 5% weight of the formulation) the cement does not exhibit appreciable bone adhesion properties. In addition, certain bio-resorbable fibers have been used as adjuncts to calcium cements. These fibers include those based on polymers formed from mixtures of lactic and glycolic acids as well as other similar polymeric materials.